FACTORS AFFECTING THE VIABILITY OF THERMOLUMINESCENCE DATING OF GLASS

The aim of this study is to achieve a better understanding of some of the factors that limit the thermoluminescence (TL) dating of glass. Using a‘model system’(lithium-disilicate samples having different levels of crystallinity from 0 to 100%), we show, first, that the TL of glass is reproducible only if the glass is not heated above its temperature glass transition and second, that there is a clear connection between the TL sensitivity and the degree of crvstallinity of the sample. We conclude that thermoluminescence is not a general dating method for archaeological glass, but it can be applied to particular glass samples that haue specified characteristics.     

THERMOLUMINESCENCE DATING OF A CRUCIBLE FRAGMENT FROM AN EARLY TIN PROCESSING SITE IN TURKEY

Archaeological exploration in the Taurus mountains at Göltepe in south-central Turkey has uncovered a site indicating the presence of extensive tin ore mining and smelling operations The most recent find of smelting crucible fragments allowed for a thermoluminescence-hased age determination spanning a late fifth to early third millennium BC date. This result is consistent with a number of radiocarbon dates derived for charcoal also found at the site. The importance of this site relates to the possible tin production and subsequent trade with southwestern Asia which would have provided this otherwise scarce ingredient to bronze technology in that area. This date is directly for crucible material and thus confirms the antiquity of tin smelting at Göltepe.     

DATING ARCHAEOMETALLURGICAL SLAGS USING THERMOLUMINESCENCE*

Thermoluminescence has a great potential for dating archaeometallurgical slags, because the smelting process leads to a well‐defined resetting of the ‘luminescence clock’. However, the complex compositions of slags have unpleasant consequences for TL measurements if the bulk slag substance is used. To overcome this problem, quartz has been separated out of slag matrices by chemical and physical procedures. The TL measurements were carried out on this defined mineral phase. This method was tested with seven slag samples from different locations and ages. In most cases, the TL ages determined show good agreement with reference data.     

CHARACTERIZATION AND THERMOLUMINESCENCE DATING OF PREHISTORIC POTTERY SHERDS FROM MILENA

This paper reports the results obtained applying absolute dating methodologies and mineralogical, petrographical and micropalaeontological characterization techniques to prehistoric pottery sherds varying in age from the Sicilian Middle Neolithic to Bronze Age. All samples came from the archaeological area of Milena (Caltanissetta, Sicily); those of the Bronze Age were found on a site with a precise stratigraphic succession. The investigation has contributed to the determination of an absolute chronology for the Milena prehistoric period. The data provide, for the first time in Sicily, absolute dates covering a wide spectrum of cultures following one another in the same area and, for the Bronze Age site, correlated to the precise stratigraphic succession. The petrographical and mineralogical analyses allowed not only the identification of the principal constituents of the pottery, but also the formulation of some hypotheses regarding the specific manufacturing techniques of different epochs. The microfacies, obtained from the presence of fossils in the groundmass of the pottery, were also analysed and compared with the microfauna present in the Miocene clays outcropping in the area. The data identified local Messinian clay as the raw material probably used in the manufacture of the pottery and also support the presence, already assumed by archaeologists, of imported Mycenaean pottery, thus supporting the dates obtained on pottery taken from the same stratum.     

AN ATTEMPT AT DATING THE SWANSCOMBE SKULL BONES USING NON-DESTRUCTIVE GAMMA-RAY COUNTING

A low-background germanium spectrometer was used to measure the gamma-ray spectra of the three parts of the Swanscombe skull. Detailed studies of the method showed that it was possible to make accurate measurements of the content of ²²⁶ Ra and ²³¹ Pa but less accurate ones of ²³⁸U and ²³⁵U. Results from the three samples were inconsistent, showing that their exposure to radioactive ground water must have been very different, although they were found close together. The uncertainty in the ratio of ²³⁴U to ²³⁸U in the ground water and the lack of knowledge of the time at which the bones acquired the uranium also prevented the deduction of any reliable dates for these specimens.     

LUMINESCENCE DATING OF POTTERY FROM LATER PREHISTORIC BRITAIN*

Dating of later prehistoric settlements relies heavily on potter; typologies in England and yet there has been little scientific dating in order to verify these typologies. In this work, luminescence dating techniques were applied directly to the pottery which forms the typological framework. Excellent agreement was obtained between the luminescence ages, and archaeological age ranges for known‐age pottery sherds with diagnostic form and surface decoration. A lower correlation, however, was found in several regions between the luminescence ages for undecorated body sherds and the archaeological assessment which was necessarily based solely on fabric, suggesting the need for reassessment of these fabric chronologies.     

THE EFFECT OF HF ACID ETCHING ON THE MORPHOLOGY OF QUARTZ INCLUSIONS FOR THERMOLUMINESCENCE DATING

The assumption of isotropic etching in hydrofluoric acid of quartz grains prepared for thermoluminescence dating has been tested by optical and scanning electron microscopy. We have found that the rate of etch is very irregular over the surface of many grains and that some grains are attacked much more severely than others. The uncertainty introduced into TL dating by this effect is discussed.     

THERMOLUMINESCENCE DATING OF STALAGMITIC CALCITE

The thermoluminescence (TL) method of dating stalagmitic calcite has been applied to twenty-seven samples from two paleolithic cave sites; Pontnewydd, Wales, and Caune de l'Arago, Tautavel, France. Environmental dose-rates were evaluated mainly by means of CaF₂ capsule burials. The ages of the stalagmitic samples were independently determined by means of the uranium series disequilibrium method. In general, good agreement is found between the TL and uranium series dates, which cover a range from approximately 15 000 to 300 000 years B.P. It is estimated that the TL method should extend to the order of a million years in good circumstances.     

URANIUM-SERIES DATING OF FOSSIL BONES FROM ALPINE CAVES

During the course of an investigation of fossil cave bear populations the uranium-series method for absolute age determination has been applied to bone material. The applicability of the method to bone samples from alpine caves could be demonstrated by the concordance of U/Th and U/Pa ages and cross-checks with the radiocarbon method. Stratigraphic agreement between bone ages and carbonate speleothetn ages also indicates the potential of the uranium-series method as a suitable tool for the age determination of fossil bones from alpine cave environments.     

URANIUM‐SERIES AND LUMINESCENCE DATING OF VOLCANIC LITHIC ARTEFACTS*

U‐series dating was used to determine the growth rate of a feldspar‐to‐clay weathering rind in a mid‐Holocene Cascade–Olcott tradition andesite core, and luminescence dating (last exposure to sunlight) was used to date fine‐grained feldspars scraped from the surfaces of similar buried artefacts from a ¹⁴C‐sediment‐dated archaeological site (45KI464) on the wet western slope of the Cascade Mountains of Washington. For U‐series dating, we measured ²²⁶Ra excess (²²⁶Ra excess =²²⁶Ra –²³⁰Th) in five stratigraphic depth controlled rind scrapings. ²³⁸U, ²³²Th and ²³⁰Th were counted by alpha spectrometry, and ²²⁶Ra and ²¹⁰Pb were counted by gamma spectrometry on each sub‐sample.     

DIRECT GAMMA-RAY SPECTROMETRIC DATING OF FOSSIL BONES: PRELIMINARY RESULTS

A non-destructive gamma-ray spectrometry was used for direct dating of fossil animal and human bones taken from an alluvial Quaternary site in northern Italy. The ages were obtained using the U-Pa method: the chronological results are in agreement with palaeofaunal indicators and taphonomic data. The ages of two samples showed concordance with the U-Th method; in a third case good agreement was also found with the radiocarbon date, thus lending credence to our modified gamma spectrometric method.     

THERMOLUMINESCENCE DATING OF MATERIALS WHICH EXHIBIT ANOMALOUS FADING

This article reports a generalised and systematic approach to the thermoluminescence (TL) dating of samples which suffer from anomalous fading. We hypothesise that the TL signal from each mineral phase is composed of a stable and an unstable portion. The decay of the unstable TL is accelerated thermally, until only stable TL remains. The dating is then carried out on this stable signal. The results, on four known-age, coeval samples, exhibiting gross anomalous fading (25-50% loss over a few days), indicate that many, if not all, samples may successfully be dated with this approach.     

LUMINESCENCE DATING OF SEDIMENTS—THE DETECTION OF HIGH EQUIVALENT DOSE GRAINS USING AN IMAGING PHOTON DETECTOR*

In this paper we describe quantitative measurements on the thermoluminescence of many single grains, made with an imaging photon detector. In several of the sediments examined a few bright grains were found which had a high equivalent dose (ED). Physical measurements made on these grains using binocular microscopy and analytical scanning microscopy enabled several possible explanations for the causes of the high ED grains to be rejected. Insufficient bleaching at deposition or the intrusion of grains from an older sediment were identified as the most probable explanation for these grains.     

FIFTY YEARS OF LUMINESCENCE DATING*

Luminescence techniques for dating both heated materials (e.g., pottery and burnt stone) and sediments have gone through three phases in the past 50 years. The first 22 years, from 1957 to 1979, were devoted to thermoluminescence (TL) techniques applied to heated material. In the next six years, from 1979 to 1985, it was found that TL dating could be applied to sediments. However, the TL signals of both quartz and feldspar grains observed for modern sediments were small, but were not zero, thus making them useful only for older sediments. A new luminescence signal that was totally zeroed by exposure to sunlight for a relatively short period of time, a few hours or less, was found; this led to the development of optically stimulated luminescence (OSL) dating techniques in 1985. Further developments have continued to the present day. Within the past 22 years, 1999 was also a year with major developments. A reliable procedure for single aliquots of quartz that have a rapidly bleached (‘fast’) OSL component was formalized and an instrument that allowed rapid measurement of equivalent doses for single grains was constructed. These developments have led to OSL becoming a major dating tool in Quaternary geology, at least for the past 100 000 years, and in archaeology, particularly as related to the dispersal of modern humans.